Surface mining is a term used to describe any type of mining process where the overlying layers of rock and soil are removed in order to extract the desired material from its deposit. Surface mining processes are performed whenever the material being mined is relatively close to the surface of the earth. Surface mining is generally a more economical process than underground mining methods. However, there are often many environmental problems associated with surface mining.[1] While there are some practices in place that reduce environmental impact from surface mining, there is growing concern about the issue of sustainability in this field.
Historical Background
Surface mining started to become a widespread practice in the U.S. in the early 1930's.[2] It was most commonly used as a method for mining coal. The demand for coal greatly increased during World War II, which led to a growth in surface mining. However, the rapid increase in coal mining contributed harmful effects on the environment.[3] The federal government recognized the need for sustainability in surface mining processes, which led to the passing of the Surface Mining Control and Reclamation Act of 1977. The main purpose of this act was to enforce a balance between environmental and agricultural protection and the economy's need for energy created by coal and other materials.[4] Currently in the U.S., about 90% of the rock and minerals and 60% of the coal that is mined is extracted through surface mining techniques.[5] Since surface mining is such a commonly practiced procedure, it continues to produce problems in the environment.
Current Surface Mining Processes
Two of the most common surface mining processes are strip mining and open-pit mining. Strip mining uses a very large machine to remove the overlying soil and rock in long, parallel strips. Some of the common machines used in this process are bucket wheel excavators, draglines, stripping shovels, and dozers.[6] Once the soil and rock are removed, the machine uses the same stripping technique to extract the material beneath the overlying layers. Open-pit mining is a method where overlying earth is removed in the form of a circular hole. Earth is excavated from the hole in a way that causes the walls of the hole to incline downwards and be stepped. The material being mined is then removed from the bottom of the hole.
Fig. 1. Strip Mining
Fig. 2. Open-Pit Mining
Advantages and Disadvantages
One advantage of these surface mining processes is that they are more economical compared to underground mining. Surface mining is able to use much larger-scale mining equipment than underground mining, which allows mining process to go quickly.[7] Also, surface mining is a safer method and involves less risk for the laborers and equipment. One disadvantage is that surface mining is only effective if the material being mined is close to the surface of the earth. Also, underground mining has less environmental risks associated with it than surface mining does.
Sustainability
Mine Reclamation
Before an area of land can be surface mined, All vegetation must be cleared from the area. While this may temporarily have a negative effect on the environment, the land can be restored through mine reclamation once the mining process is finished. In order for reclamation to be successful, the topsoil that is initially removed before surface mining begins must be saved. Once the mining process is completed, this topsoil is placed back into the area it was removed from.[8] Then, the topsoil is reseeded with its native crops, vegetation, and trees that it contained before the mining process destroyed the land. While this process greatly benefits the species living in the area, it involves a great amount of maintenance and monitoring for several years to ensure that the land is properly restored to its natural state.[9] For surface mines that require a significant amount of land to be cleared, the reclamation process is often a worthwhile option. It is also beneficial to consider putting a surface mining site in an area with existing infrastructure.[10] This reduces the amount of reclamation that would need to occur after the surface mining is complete.
Fig. 3. Surface mining area after mine reclamation
Intended Improvement
A common way that people are looking to improve sustainability in surface mining is through modifications to mining vehicles. One example is an attempt to develop electricity powered mining machines. Instead of using diesel fuel, the vehicles would use electric drive powered by a generator.[11] This would potentially eliminate pollution caused by gasoline emissions from these vehicles. Also, gearing and heating technologies are being developed for mechanical drive trucks, which would significantly increase their efficiency in poor ground conditions.[12]
Successful Application
An example of a successful improvement in surface mining sustainability occurred in Jamaica. A company called Alcoa Jamalco developed a rope conveyor belt system that generates electricity as it transports bauxite out of a mine.[13] This electricity is used to power the mine as well as Jamaica's power network. In its first four years of operation, this conveyor belt saved approximately $1.5 million in energy costs.[14] The belt also helps the environment, since it eliminates the need for trucks to transport bauxite. This reduces the amount of carbon dioxide and dust emissions that enter the atmosphere.[15]
Overview
Surface mining is a term used to describe any type of mining process where the overlying layers of rock and soil are removed in order to extract the desired material from its deposit. Surface mining processes are performed whenever the material being mined is relatively close to the surface of the earth. Surface mining is generally a more economical process than underground mining methods. However, there are often many environmental problems associated with surface mining.[1] While there are some practices in place that reduce environmental impact from surface mining, there is growing concern about the issue of sustainability in this field.
Historical Background
Surface mining started to become a widespread practice in the U.S. in the early 1930's.[2] It was most commonly used as a method for mining coal. The demand for coal greatly increased during World War II, which led to a growth in surface mining. However, the rapid increase in coal mining contributed harmful effects on the environment.[3] The federal government recognized the need for sustainability in surface mining processes, which led to the passing of the Surface Mining Control and Reclamation Act of 1977. The main purpose of this act was to enforce a balance between environmental and agricultural protection and the economy's need for energy created by coal and other materials.[4] Currently in the U.S., about 90% of the rock and minerals and 60% of the coal that is mined is extracted through surface mining techniques.[5] Since surface mining is such a commonly practiced procedure, it continues to produce problems in the environment.
Current Surface Mining Processes
Two of the most common surface mining processes are strip mining and open-pit mining. Strip mining uses a very large machine to remove the overlying soil and rock in long, parallel strips. Some of the common machines used in this process are bucket wheel excavators, draglines, stripping shovels, and dozers.[6] Once the soil and rock are removed, the machine uses the same stripping technique to extract the material beneath the overlying layers. Open-pit mining is a method where overlying earth is removed in the form of a circular hole. Earth is excavated from the hole in a way that causes the walls of the hole to incline downwards and be stepped. The material being mined is then removed from the bottom of the hole.
Advantages and Disadvantages
One advantage of these surface mining processes is that they are more economical compared to underground mining. Surface mining is able to use much larger-scale mining equipment than underground mining, which allows mining process to go quickly.[7] Also, surface mining is a safer method and involves less risk for the laborers and equipment. One disadvantage is that surface mining is only effective if the material being mined is close to the surface of the earth. Also, underground mining has less environmental risks associated with it than surface mining does.Sustainability
Mine Reclamation
Before an area of land can be surface mined, All vegetation must be cleared from the area. While this may temporarily have a negative effect on the environment, the land can be restored through mine reclamation once the mining process is finished. In order for reclamation to be successful, the topsoil that is initially removed before surface mining begins must be saved. Once the mining process is completed, this topsoil is placed back into the area it was removed from.[8] Then, the topsoil is reseeded with its native crops, vegetation, and trees that it contained before the mining process destroyed the land. While this process greatly benefits the species living in the area, it involves a great amount of maintenance and monitoring for several years to ensure that the land is properly restored to its natural state.[9] For surface mines that require a significant amount of land to be cleared, the reclamation process is often a worthwhile option. It is also beneficial to consider putting a surface mining site in an area with existing infrastructure.[10] This reduces the amount of reclamation that would need to occur after the surface mining is complete.Intended Improvement
A common way that people are looking to improve sustainability in surface mining is through modifications to mining vehicles. One example is an attempt to develop electricity powered mining machines. Instead of using diesel fuel, the vehicles would use electric drive powered by a generator.[11] This would potentially eliminate pollution caused by gasoline emissions from these vehicles. Also, gearing and heating technologies are being developed for mechanical drive trucks, which would significantly increase their efficiency in poor ground conditions.[12]
Successful Application
An example of a successful improvement in surface mining sustainability occurred in Jamaica. A company called Alcoa Jamalco developed a rope conveyor belt system that generates electricity as it transports bauxite out of a mine.[13] This electricity is used to power the mine as well as Jamaica's power network. In its first four years of operation, this conveyor belt saved approximately $1.5 million in energy costs.[14] The belt also helps the environment, since it eliminates the need for trucks to transport bauxite. This reduces the amount of carbon dioxide and dust emissions that enter the atmosphere.[15]